• Journal of Korea Multimedia Society
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• v.16 no.5
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• pp.601-609
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• 2013

One of the most serious factors constraining the next generation cellular mobile consumer communication systems will be the severe co-channel interference experienced at the cell edge. Such a capacity-degrading impairment combined with the limited available spectrum resource makes it essential to develop more spectrally efficient solutions to enhance the system performance and enrich the mobile user's application services. This paper proposes a unique hybrid method of frequency hopping (FH) and subcarrier-reuse-partitioning that can maximize the system capacity by efficiently utilizing the available spectrum while at the same time reduce the co-channel interference effect. The main feature of the proposed method is that it applies an optimal combination of different frequency reuse factors (FRF) and FH-subcarrier allocation patterns into the partitioned cell regions. From the simulation results, it is shown that the proposed method can achieve the optimum number of subcarrier subsets according to the frequency-reuse distance and results in better performance than the fixed FRF methods, for a given partitioning arrangement. The results are presented in the context of both blocking probability and BER performances. It will also be shown how the proposed scheme is well suited to FH-OFDMA based cellular systems aiming at low co-channel interference performance and optimized number of subcarriers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.335-341
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• 2013

The variation of systematic bias errors in the wind tunnel testing has been studied. A Design of Experiments(DOE) approach to an experimental study of fuselage drag and stability characteristics of a helicopter configuration was applied. When forces and moments measured in one time block differ significantly from measurements made in another time block under assumption that sample observations can be expected to yield same results within permissible measuring errors. The practical implication of this paper is that the systematic error can not be assumed not to exist. The those error reduction could be achieved through the process of randomization, blocking, and replication of the data points.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.227-227
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• 2014

OLED 소자에 사용되는 유기물들은 대부분 전자에 비해 정공의 이동속도가 매우 빨라 소자 효율의 손실이 일어난다. 본 연구에서는 이러한 전하 이동도의 불균형에 의한 OLED 소자 성능의 감소를 개선하기 위해 HBL (hole blocking layer) 물질로 BCP (HOMO : 6.5 eV, LUMO : 2.83 eV)를 도입하였다. 그러나 BCP의 LUMO 값이 약 3 eV를 가지기 때문에 전자의 이동에 영향을 미치는 것으로 예상되어 더 높은 효율을 가지는 소자를 제작하기 위해 host 물질을 상용물질(PGH02)로 교체하였다. PGH02의 HOMO 값은 약 5.86 eV로 소자에 사용된 HTL (hole transport layer)의 HOMO 값(5.54 eV)에 비해 높은 값을 가지기 때문에 HBL의 역할 역시 가능하여 소자의 성능이 상당히 개선되는 것을 확인할 수 있었다. 또한 전하 이동도의 균형을 맞추기 위해 ETL 물질로는 기존에 많이 사용되고 있는 Alq3 (${\mu}{\sim}10-5cm2/Vs$)에 비해 이동도가 10배 이상 빠른 Bebq2 (${\mu}{\sim}10-4cm2/Vs$)를 사용하였다. HTL (hole transport layer) 물질로는 상용물질(LHT 259)를 사용하였고, LHT 259의 전하 이동도는 FET (field effect transistor)를 제작하여 측정하였다. 이를 기반으로 하여 ETL과 HTL의 두께를 조절하여 전하 이동도가 균형을 이루는 OLED 소자를 제작하기 위해 실험을 진행하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.453.1-453.1
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• 2014

Fluorine-doped tin oxide (FTO), which is commonly used in dye-sensitized solar cells (DSSCs), is a promising material of transparent conducting oxides (TCOs) because of advantages such as high chemical stability, high resistance, high optical transparency (>80% at 550nm), and low electrical resistivity (${\sim}10-4{\Omega}{\cdot}cm$). Especially, dye-sensitized solar cells (DSSCs) have been actively studied since Gratzel's research group required FTO substrate as a charge collector. When FTO substrates are used in DSSCs, photo-injected electrons may experience recombination at interface between dye-bonded semiconductor oxides ($TiO_2$) on FTO substrate and the electrolyte. To solve these problems, one is that because recombination at FTO substrate cannot be neglected, thin $TiO_2$ layer on FTO substrate as a blocking layer was introduced. The other is to control the morphology of surface on FTO substrate to reduce a loss of electrons. The structural, electrical, and optical characteristics of morphology controlled-FTO thin films as TCO materials were analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Hall Effect Measurement, and UV spectrophotometer. The performance of DSSCs fabricated with morphology controlled FTO substrates was performed using Power Conversion Efficiency (PCE). We will discuss these results in detail in Conference.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.3
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• pp.678-683
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• 2008

Aconitum pseudo-laeve var. erectum has traditionally been used for the treatment of water retention in the body. Administration of the aqueous extract of Aconitum pseudo-laeve var. erectum has the efficiency of anti-inflammatory activity and modulates the intestinal immune system. However, the mechanism of anti-inflammatory action of Aconitum pseudo-laeve var. erectum has not been clarified yet. In the present study, the effect of Aconitum pseudo-laeve var. erectum against LPS-stimulated expressions of COX-2 and iNOS in cells of the murine RAW 264.7 macrophages was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, reverse transcription- polymerase chain reaction (RT-PCR), PGE2 immunoassay, and NO detection. The results of the present study indicate that Aconitum pseudo-laeve var. erectum is a potent inhibitor of the LPS-induced NO and $PGE_{2}$ production by blocking iNOS and $NF{\kappa}B$ activation in RAW 264.7 macrophages. These findings suggest that Aconitum pseudo-laeve var. erectum is a potential therapeutic for the treatment of inflammatory syndrome.

• Parasites, Hosts and Diseases
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• v.44 no.1 s.137
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• pp.35-41
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• 2006

Protozoan parasites of the genus Leishmania cause a number of important human diseases. One of the key determinants of parasite infectivity and survival is the surface glycoconjugate lipophosphoglycan (LPG). In addition, LPG is shown to be useful as a transmission blocking vaccine. Since culture supernatant of parasite promastigotes is a good source of LPG, we made attempts to characterize functions of the culture supernatant, and membrane LPG isolated from metacyclic promastigotes of Leishmania major. The purification scheme included anion-exchange chromatography, hydrophobic interaction chromatography and cold methanol precipitation. The purity of supernatant LPG (sLPG) and membrane LPG (mLPG) was determined by SOS-PAGE and thin layer chromatography. The effect of mLPG and sLPG on nitric oxide (NO) production by murine macrophages cell line (J77 4.1 A) was studied. Both sLPG and mLPG induced NO production in a dose dependent manner but sLPG induced significantly higher amount of NO than mLPG. Our results show that sLPG is able to promote NO production by murine macrophages.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.2
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• pp.18-25
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• 2003

The adsorption of co-cationic dual polymer system was investigated as was the fiber dispersion stability of a paper stock suspension. Polyaluminum chloride(PAC) and polyamidoamine epichlorohy-drin(PAE) polymers were used as wet-end additives. The adsorbed amounts of PAE polymer in a wet stock were measured by using polyelectrolytic PCD titration. The sheet forming experiments were carried out in a standard handsheet machine. Fiber dispersion stability and relative retention were evaluated in terms of M/K non-uniformity index and sheet basis weight, respectively. The PAE polymer adsorption of Langmuir-isothermal type decreased with increasing PAC addition level. The combination of the two cationic polymers presumably exerts a site-blocking effect by the low molecular weight PAC which gives a partial charge neutralization at a minimum level of addition. From a thermodynamic view point of PAE adsorption, an increase in adsorption entropy and a decrease in train number suggests that the PAR polymer has an extended conformation structure that potentially leads to an enhancement of the fiber dispersion stability. This conclusion is supported by handsheet experiments that examined the PAC-PAE dual polymer effects on the sheet formation and retention.

• Korean Journal of Medicinal Crop Science
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• v.17 no.1
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• pp.8-14
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• 2009

Pueraria lobata (Willd.) Ohwi was investigated to check its modulatory effects on the activation of macrophages upon inflammatory conditions treatment. For this purpose, we examined several inflammatory responses such as nitric oxide (NO) production, reactive oxygen species (ROS) generation, cytoprotection and phagocytosis under the treatment of methanol extract from P. lobata (Pl-ME). Pl-ME dose-dependently blocked NO production in lipopolysaccharide (LPS)- stimulated RAW264.7 cells but not sodium prusside (SNP)-generated NO release. The NO inhibition seemed to be due to blocking inducible NO synthase (iNOS), since Pl-ME suppressed its expression in a NF-${\kappa}B$-independent manner. Similarly, this extract also effectively protected RAW264.7 cells from LPS-induced cytotoxicity. However, Pl-ME did not block ROS generation and rather it enhanced. Finally, this extract negatively modulated FITC-dextran uptake. Therefore, our data suggested that Pl-ME may be involved in negatively regulating some macrophage-mediated inflammatory responses such as NO production and phagocytic uptake.

• 한국전자현미경학회:학술대회논문집
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• 2007.05a
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• pp.71-74
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• 2007

천연 대마섬유의 UVB 차단 효과를 조사하고자 mouse를 4개의 그룹으로 구분하여 자외선을 조사한 뒤 외이의 조직절편을 제작하여 비교 분석하였다. 자외선을 직접 조사한 실험군[U], 대마섬유로 차단한 뒤 자외선을 조사한 실험군[H], 폴리에스테르 섬유로 차단한 후 자외선을 조사한 실험군[P], 자외선을 조사하지 않은 대조군[C]으로 나누어 실험한 후 광학현미경하에서 피부 조직의 변화를 관찰하였다. 대조군[C] 외이조직의 상피세포층 두께는 $16.3\;{\mu}m$이었지만, 자외선을 직접 조사한[U]군의 상피세포층은 $65.4\;{\mu}m$, [H]군은 $33.3\;{\mu}m$, [P]군은 $41.0\;{\mu}m$의 두께 변화를 보였다. 또한, 정상적인 외이의 상피세포의 단면적은 $22.0\;{\mu}m^2$이었으나, 자외선을 직접 조사한 [U]군의 상피세포층은 $37.7\;{\mu}m^2$, [H]군은 $30.1\;{\mu}m^2$, [P]군은 $30.2\;{\mu}m^2$이었다. 따라서 천연 대마섬유와 합성 폴리에스테르섬유 모두 UVB를 차단하는 능력을 갖고 있지만 전자가 후자보다 더 효과적으로 UVB를 차단함을 알 수 있었다.

• Journal of the Korean Ceramic Society
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• v.45 no.6
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• pp.324-330
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• 2008

Activated carbon/$TiO_2$ (AC/$TiO_2$) composites modified with different concentrations of Fe were prepared. The $N_2$ adsorption data showed that the composites had decreased surface area compared with the pristine activated carbon. This indicated the blocking of the micropores on the surface of AC, which was further supported by observation via SEM. XRD results showed patterns for the composites and an anatase typed titanium dioxide structure with a small part of rutile in a higher Fe concentration (> 1.0 mol/L). EDX results showed the presence of C and, O, with Ti peaks on the composites of Fe-AC/$TiO_2$ with relatively lower Ti concentration, which may be due to the higher Fe concentration incorporated into the composites. Subsequently, the photocatalytic effects on methylene blue (MB) were investigated. The improved decomposition of MB showed the combined effects of adsorptions and photodegradation. Especially, the composites modified by Fe revealed enhanced photodegradation behaviors of MB.